1. Technical Field
The present invention, in a press part of a paper machine, relates to a belt for a shoe-press which goes around while pressurizing a press roll from a press shoe side to remove water from wet paper. Further specifically, the present invention relates to a belt for a shoe-press which is arranged to have a specific surface condition of water drain grooves formed on the surface thereof.
2. Description of the Related Art
In a paper making process in paper manufacturing, water contained in a wet paper is absorbed by transferring water in the wet paper to a felt by pressurizing the felt running between a press roll of a paper machine and a press shoe together with the wet paper placed thereon by a shoe-press mechanism of the paper machine.
A shoe-press mechanism is one widely used in a press device of a paper manufacturing machine, in which when a press belt runs between a press roll of the paper machine and a press shoe, the belt runs accompanying with rotation of the press roll while being pressurized by the press shoe side.
The press belt or the shoe-press belt normally has such a structure that polyurethane resin layers are formed on both sides of a base cloth. The belt is usually provided with water drain grooves on a felt side surface enabling absorption of water squeezed out in a press part. It is important to drain water squeezed out in the press part of a paper machine effectively, and therefore an arrangement to extend many grooves on the felt side surface of the shoe-press belt is considered to be an effective method.
The belt, however, is pressurized intensively in the press part of the paper machine, especially in the shoe-press, which causes wear of the belt surface for the wet paper or deformation of the belt grooves due to the provision of water drain grooves. Particularly, there has arisen a problem of the occurrence of cracks at the groove portions. Therefore, the configuration of the grooves has to be suitable for effective draining of squeezed water as well as being capable of restraining groove deformation and the occurrence of cracks to a minimum.
A number of methods to improve groove configuration have been attempted particularly as a method to restrain deformation of grooves, and to prevent the occurrence of cracks at the root of the grooves. For example, one having rounded roots of grooves with a side wall thereof maintaining a divergence angle of 5 degrees to 15 degrees (Patent document 1), one having groove a configuration that gradually widens towards an upper part thereof (Patent documents 2 and 4), one having a concave curved top surface of a belt with grooves (Patent document 3), one having grooved side walls which are curved towards outside (Patent document 5), one having groove side walls which have inclined surfaces in the opening area, or have spherical portions which extend so as to correspond to the predetermined curve (Patent document 6), and the like can be listed.
[Patent document 1] Publication of Patent Application No. Hei 10-510594
[Patent document 2] Japanese Utility Model Publication No. Hei 1-36960
[Patent document 3] Japanese Patent Application Laid-open No. Sho 64-61591
[Patent document 4] Japanese Utility Model Application Laid-open No. Sho 61-7598
[Patent document 5] Japanese Patent Application Laid-open No. 2001-98484
[Patent document 6] Japanese Patent Application Laid-open No. Hei 11-335992